Wheat is the first important and strategic cereal crop for the majority of the world's population and is the most important staple food of about two billion people (36% of the world population). Worldwide, wheat provides nearly 55% of the carbohydrates and 20% of the food calories consumed globally (Breiman and Graur, 1995). Wheat exceeds in acreage and production every other grain crop (including rice, maize, etc.) and is cultivated over a wide range of climatic conditions. The understanding of wheat genetics and genome organization using molecular markers is of great value for genetic and plant breeding purposes.
Proteins are the most important component of wheat grain governing its end-use value. Grain storage protein (GSP) composition is known to determine dough cohesiveness and visco-elasticity. The most abundant GSPs in wheat are the gluten-forming gliadins and glutenins, which account for 60% to 80% of total grain protein.
Coeliac disease is a condition in which the lining of the small intestine is damaged by gluten, a mixture of different storage proteins found in the starchy endosperm of wheat, rye and barley grains as well as in closely related species. The gluten matrix consists of approximately equal mixtures of gliadin and glutenin proteins. Coeliac disease is primarily caused by the gliadin proteins. Specifically, in this disease the villi of the small intestine are destroyed and the lining becomes flattened, seriously impairing nutrient absorption. Typical symptoms are weight loss, foul-smelling diarrhea, vomiting, abdominal pain and swelling of the legs. The only cure currently available is a life-long gluten-free diet strictly avoiding all food and pharmaceutical compositions containing wheat, rye and barley. In addition to Coeliac disease, a number of humans suffer from general intolerance to glutens. The range of this intolerance varies greatly although there are no clear clinical symptoms as in coeliac disease.
Thus, there is a clinical need to reduce consumption of gluten and a corresponding need to develop wheat and other grains with reduced gluten. Although the need has been long felt, the identification of mutations in wheat genes that reduce gluten has proceeded slowly because, among other possible reasons, there is limited genetic diversity in today's commercial wheat cultivars and the wheat genome is complex. Bread wheat is a hexaploid, with three complete genomes termed A, B and D in the nucleus of each cell. Each of these genomes is almost twice the size of the human genome and consists of around 5,500 million nucleotides. On the other hand, durum wheat, also known as macaroni wheat or pasta wheat (Triticum durum or Triticum turgidum subsp. durum), is the major tetraploid species of wheat of commercial importance, which is widely cultivated today. Durum wheat has two complete genomes, A and B, and is widely used for making pasta.
The inventors have identified genes, wherein mutations and modification of said genes produce reduced gluten grains.